Gel electrophoresis is one of the most common methods for rapid and simple protein analysis.
Electrophoresis has been used for a long time to separate charged molecules according to their difference in migration rate under the influence of an electrical field. An electrophoresis system is standard equipment in almost every lab in the world.
Traditionally, the molecules are stained in the gel after electrophoresis by more or less selective dye stains or by precipitation of colloidal metal particles.
The molecules to be separated may also be labelled with, for example a radioactive or fluorescent label, for detection after the electrophoresis.
Today it is most common to avoid the use of radioactivity in favour of fluorescent labelling. However, the electrophoretic backings used to carry the electrophoretic slab gel are in many cases fluorescent per se which disturbs the detection procedure.
Commonly used electrophoretic support films, such as polyethylene terephthalate (PET) comprise an adhesive layer between the support film and the hydrogel. This type of backed gels, for example PHAST™ gels, function satisfactorily for relatively large amounts of fluorescence labelled biomolecules but their inherent fluorescence is too high which disturbs and hinders the detection of low amounts of biomolecules after slab gel electrophoresis.
Since this can lead to false negative results in for example a diagnostic assay it is very important to be able to detect very low amounts of biomolecules in for example a biological sample. Another case is in pharma research where most of the pharmacologically interesting proteins occur at very low concentrations compared to high abundance proteins, such as plasma albumin.
It would be desirable to have a gel without backing for blotting applications, such as Western blot applications. PHAST™ gels are at the present possible to use in Western blot applications although with some difficulties. Since the gel is firmly attached to the plastic backing the gel needs to be removed from the backing using a “gel remover”. This is not user friendly and introduces variability to the experiment.
To solve this problem, electrophoretic supports of glass have been used. Glass enables imaging of low amounts of fluorescence labelled samples. However, glass as electrophoretic support is not desirable of space, weight and safety reasons. Furthermore, electrophoretic glass supports are not suitable for production of large amounts of pre-swollen ready to use gels. It would be desirable to have pre-swollen ready to use gels which are non-fragile, enable fluorescence detection of low sample amounts and occupy a minimum of space.
Another solution to avoid the problem with fluorescent background in detection of fluorescence labelled electrophoresis samples, has been described in WO 04/106911. Here a low fluorescent polymer film is used so support the hydrogel. The hydrogel is attached to the polymer film by an adhesive layer. For performing Western blotting after electrophoresis, the polymer film has to be removed from the gel before the blotting procedure.
Thus, the detection problem with fluorescence labelled biomolecules following slab gel electrophoresis and the transferring problem thereafter to Western blotting still need to be solved.